The known biocide, bis trichloromethyl sulfone, has heretofore been prepared by various routes, one being the oxidation of dimethyl sulfoxide with sodium hypochlorite. The bis trichloromethyl sulfone product was then separated, and, typically, dried.
Since bis trichloromethyl sulfone is poorly soluble in water, it was heretofore apparently customary to dissolve this material in an organic solvent medium for which it was necessary to isolate bis trichloromethyl sulfone once after the synthesis reaction and dry it. Such prior art procedure suffers from serious disadvantages. For one thing, the aqueous brine solution inherently resulting as a by-product when sodium hypochlorite is used to oxidize dimethyl sulfoxide to bis trichloromethyl sulfone must be disposed of, which presents serious environmental pollution problems, particularly since the level of sodium chloride in the brine can approach saturation levels (e.g. about 30 weight percent). For another thing, the rewetting and suspending of bis trichloromethyl sulfone powder in water to make an emulsion, represents a time consuming, labor consuming operation. In addition, when it is desired to blend with a bis trichloromethyl sulfone solution in organic solvent one or more additional biocides to broaden the spectrum of biocidal activity for the resulting composition, an entire series of special formulation preparation procedures were heretofore conventional and apparently considered essential to the making of a desired liquid composition containing dissolved bis trichloromethyl sulfone. See for example, U.S. Pat. No. 3,426,134 to Shema, Reilly, and Kubasko.
There are growing objections to the use of organic solvents in formulating biocides. For one thing, solvents cause ecological problems. Thus, organic solvents can cause acceleration in the ability of a biocide to penetrate human skin so that in the case of spills or accidental contact, the danger to human life is increased by the presence of such solvents. Water based systems do not penetrate skin as rapidly, and therefore, water based systems are somewhat safer to use. For another thing, solvents raise economic problems, owing to recent raises in the prices of organic solvents commonly used in formulating biocides. For still another thing, solvents can offer processing problems, so that the effect is to increase the cost of biocidal formulations containing organic solvents. Thus, for example, previously bis trichloromethyl sulfone was produced and separated (dried) before ever being formulated in non-aqueous solvent systems; brine generated in production thus presented disposal problems, as indicated above. Control of solvent vapors during formulation preparation can be a problem.
It has now been discovered that bis trichloro methyl sulfone is unexpectedly well adapted for emulsification to form emulsions of the oil-in-water type. It happens that this material melts at a relatively low temperature (about 35.degree. C) and can be warmed to higher temperatures without decomposition. Thus, when the liquid material is heated to about 60.degree. to 70.degree. C, and agitated with a surfactant (or emulsifier) in the presence of deionized water, it has now been discovered that a true liquid/liquid emulsion of the oil in water type results which contains absolutely no organic solvent.
It has been now further discovered that bis trichloromethyl sulfone surprisingly can be emulsified in the brine water produced during its synthesis by the route above indicated. It is generally difficult to emulsify materials in brine. The high ionic content in brine works against emulsification therein because such tends to upset the delicate interaction of electric charges permitting formation of the dispersed phase in the continuous phase. Indeed, an increase in ion content is a conventional means used to coagulate an emulsion. It is unexpected that coagulation does not occur in such brine water of bis trichloromethyl sulfone emulsified therein, and the result could not have been predicted.
Emulsification of bis trichloromethyl sulfone in its own (waste) brine water not only saves the trouble and expense of further separating and drying the material, as heretofore done in this art, but also solves a difficult ecological problem of disposing of the brine water. Such emulsification avoids the need to isolate the product out of the reaction and then going back into a reactor for formulation. Such emulsification avoids altogether the use of organic solvents. Further, other biocides can be readily compounded with the bis trichloromethyl sulfone in a product emulsion without adversely affecting emulsion desired characterstics, thereby broadening the spectrum of biocidal activity for a resulting mixed system. A product emulsion can generally be infinitely diluted which permits such to be employed in the end use applications directly without intermediate treatment or dilution where the bis trichloromethyl sulfone is used at a rate of the order of parts per million in a water system (e.g. in cooling towers and the like). Surprisingly, a product emulsion of this invention containing brine water has improved freeze/thaw stability over such an emulsion containing no dissolved salts.
Thus, there has now been discovered a new technique for preparing bis trichloromethyl sulfone aqueous emulsions of the oil in water type which avoids the disadvantages associated with the prior art technology and enables one to prepare new and very useful emulsions of bis trichloromethyl sulfone. These new emulsions can be prepared so as to contain bis trichloromethyl sulfone over a variety of concentrations, and the technique involved readily permits the introduction of other biocides into the product emulsion during preparation thereof in a simple but convenient and step-saving manner.